1. Field of the Invention
The present invention relates to a strip-like brush seal having a plurality of thin plates that are processed to have thin, cantilever beams at their one end and relates to a brush seal device, for sealing between a rotational shaft and a mating component movable relatively thereto, for example in an aircraft and a gas turbine. More particularly, the present invention relates to a technical field of a brush seal and a brush seal device capable of following the rotation or minute variation of one component with respect to other component to deform during relative movement for effectively sealing between both components.
2. Description of the Related Art
There exists, as shown in FIG. 12, a brush seal device 100 as one related art of the present invention. FIG. 12 is a sectional view of a brush seal device 100 mounted between a rotational shaft 120 and a casing 110 through which the rotational shaft 120 passes. The casing 110 is a component of a steam turbine or gas turbine. The brush seal device 100 separates the casing 110 and the rotational shaft 120 so as to seal fluidly.
In FIG. 12, the brush seal device 100 is formed in a ring shape and attached to a channel section 112 of the casing 110. Main components of the brush seal device 100 are a brush seal 109, a back plate 102 and a retaining plate 103. In the brush seal 109, a number of bristles 101 in the form of a wall are arranged circumferentially, and one end of the bristles are coupled together to form an attachment section 104. The free end face 105 as the other end of the brush seal 109 faces the rotational shaft 120. The diameter of each bristle 101 used in general is 0.02 to 0.5 mm. However its sealing ability will be reduced because the brush seal device is formed of linear bristles 101 in the form of a wall that has been merely brought together. In order to overcome such a drawback the thickness of the wall formed with the bristles 101 must be increased and thus tens of thousands or hundreds of thousands of bristles 101 are necessarily used.
An annular back plate 102 is located on one side face of the brush seal 109 with its side face 108 contacting the one side face of the brush seal 109 and bears each of the bristles 101 against the action of the sealed fluid pressure.
A retaining plate 103 formed as a ring plate is disposed integrally on the other side face of the brush seal 109 to sandwich, in cooperation with the back plate 102, the brush seal 109 on its attachment section 104 side. The retaining ring 103 has a small thickness in its radial direction so that the brush seal 109 is exposed to allow the brush seal 109 to deform corresponding to the contact of the rotational shaft 120 therewith.
The back plate 102, the attachment section 104 of the brush seal 109 and the retaining plate 103 are welded at one end together to form into a connecting section 106.
In FIG. 12, the rotational shaft 120 shown by an actual line is in a state that the rotational shaft 120 is normally fitted without oscillation and every bristle 101 extends straight and inclines in the rotating direction, relative to the radial direction of the rotational shaft 120. Accordingly, the free end face 105 will be precisely finished after fabrication of the brush seal 109 so as to fit the rotational shaft 120 normally. It is however difficult to process the free end face 105 because tens or hundreds of thousands of bristles 101 arrayed in the form of a wall in the free end face 105 are apt to deform.
When the rotational shaft 120 then contacts the brush seal 109, the brush seal 109 is pressed against the rotational shaft 120 while its tilt angle is increased. At the same time there are created gaps between neighboring bristles 101 due to their movement and/or deformation.
In this state, as shown in FIG. 12, if the pressure of the sealed fluid is a high pressure P1, the differential pressure (P1-P2) between P1 and a low pressure P2 is increased, and then the gaps formed between neighboring bristles 101 will be further enlarged, resulting in the sealing ability to be worsened.
FIGS. 13 and 14 are partial front views of the brush seal 109, seen radially from its inner side.
In FIGS. 13 and 14, if the sealed fluid enters the gaps between straight bristles 101, each bristle 101 arranged as shown in FIG. 13, seen from their inner circumferential side, is pushed aside such that each gap width between the bristles 101 is increased as shown in FIG. 14, and as a result the sealed fluid leaks from those gaps.
If neighboring bristles 101 inclined are separated apart each other by the pressure described above, one of the bristles 101 separated apart tends to displace to reduce its tilt angle, and it is therefore deformed such that its length along the radial direction is long. Accordingly, the pressure applied to the rotational shaft 120 is increased to cause wear. This wearing action will be accelerated as the thickness of the bundle of the bristles 101 becomes large for improving the sealing ability.
In this state, with the increase of the gap C formed between the free end face 105 of the bristles 101 and the rotational shaft 120 (Refer to the rotational shaft shown by a phantom line in FIG. 12) on the diametrically opposite side, the sealed fluid leaks from the gap C.
Further, there exists a seal device as another related art, as shown in FIG. 15. In the figure, thin plate like leaves are piled as a seal 209 along the circumferential direction of the rotational shaft 120 to seal between a high pressure side area P1 and a low pressure side area P2.
Outer circumferential portion of the seal 209 of plate like leaves is brazed to form an attachment section 104. Then the seal 209 is attached to the channel section of the casing 110 through the brazed attachment section 104.
Also, a back plate 102 is disposed on the side face of the seal 209 at the low pressure side area P2, a retaining plate 103 is disposed on the side face at the high pressure side area P1, and both the plates 102 and 103 retain both sides of the seal 209, respectively.
However, when the rotational shaft 120 eccentrically presses against the seal 209 formed in the above manner, the seal 209 having piled thin plate like leaves to form an annular body has no space for accommodating own elastic deformation and thus the spring constant corresponding to the resilient deformation is increased. It is therefore difficult for the seal 209 to follow the eccentric behavior of the rotational shaft 120.
Further, in the seal 209 in which thin plate like leaves are piled in the direction of the action of the sealed fluid pressure, gaps are forced to create between two neighboring plates. This causes a problem relating to its sealing ability for fluid leakage.
Moreover, the seal 209 forming an annular body includes hundreds of thousands of thin plate like leaves that are piled in the annular direction. Therefore, it is extremely difficult to fabricate the seal 209. Further, as the length along the outer circumference of the annular body of the seal 209 is longer than that along the inner circumference, spacers for compensating the difference in length theretween are necessarily disposed between thin plate like leaves at their outer circumferential sides. However, gaps still remain between the surfaces of the piled plate like leaves. In this viewpoint, there also exists the problem of sealing ability. Also, in this constitution whose flexibility may be reduced, the free end face 105 of the seal 209 be worn quickly due to its worsened elastic response.
In the brush seal device 100 constituted as described above, when the sealed fluid acts on the bristles 101, gaps are created therebetween, as shown in FIG. 14, because the bristles 101 are randomly gathered together to form a bundle in the shape of a wall.
Further, when the rotational shaft 120 contacts the brush seal 109 as a result of oscillation or vibration, the brush seal 109 is pressed against the rotational shaft 120, and at the same time its tilt angle is increased, as shown in FIG. 12. If the number of the bristles 101 is increased in order to improve the sealing ability, the elastically responsive deformation of each bristle 101 will be worsened during contacting the rotational shaft 120, causing to promote the wear on the contacting surfaces. The sealing ability will be further reduced.
Also, in the seal 209 having thin plate like leaves piled to contact each other in the direction of the action of the sealed fluid, gaps are apt to be created between thin plate like leaves, causing leakage of the sealed fluid. Additionally, as the flexibility of the free end 105 of the seal 209 is limited, it will be worn quickly.
The present invention has been made in consideration of the problems as mentioned above, and an technical problem of the invention is to allow to easily pile brush seal units one by one to complete a brush seal so that the slits defining thin beams of a brush seal unit are blocked by the thin beams of a neighboring brush seal unit placed in position.
Another technical problem is to provide easy designing, processing and fabrication. Still another technical problem is to reduce the manufacturing and assembly costs of the brush seal.
Further it is still another technical problem to improve the sealing ability even if the piling thickness of the brush seal is thin, and to improve elastic deformation of the brush seal with respect to the depression force applied by the rotational shaft and to reduce wear on the brush seal by the rotational shaft.
In addition, it is yet another technical problem to provide the brush seal with good ability of the brush seal to follow in response to the relative displacement between the brush seal and the outer circumference of the rotational shaft for improving the sealing ability.
The present invention has been made to solve the problems as mentioned above, and technical means for solving the problems are constituted as below.
A brush seal of first preferred embodiment according to the present invention is a brush seal having piled brush seal units and mounted on one of two components that are relatively rotated, for sealing the clearance given between the two components, comprising: a plurality of the brush seal units, each having a strip-like brush section on the side facing the other component and having a base plate section on the side opposing the brush section side, the brush section being formed with thin beams each of which is between two slits, and the base plate section being fixed to the one component; and a plurality of positioning sections located in the base plate section of each brush seal unit; wherein each pitch dimension of each positioning section is determined so that the positioning sections, the slits and the thin beams are formed in such a physical relationship that, when the brush seal units are piled, strip-like slits and thin beams overlap each other by relatively displacing by one pitch the neighboring brush seal units.
In the brush seal of the first embodiment of the present invention, neighboring brush seal units are piled such that their positioning sections are relatively displaced by one pitch. Therefore, the slits of one brush seal unit overlap the thin beams of the neighboring brush seal unit, while the beams of the one brush seal unit overlap the slits of the neighboring one, thereby to seal the slits.
Then another brush seal unit is piled with one pitch displacement in the positioning sections relative to one of the two brush seal units that have been already piled. The slits and thin beams of those brush seal units overlap in the same manner as described.
It is extremely difficult for an assembly machine to pile the brush seal units with the thin beams and slits overlapping precisely each other. However, a piling condition effective to sealing ability is easily achieved with such positioning sections.
Accordingly, it becomes possible to improve the sealing ability of the brush seal even if the number of the brush seal units to be piled is less. Additionally, it is expected that frictional wearing is effectively prohibited as the brush seal has flexibility due to less number of the piled brush seal units and can deform elastically corresponding to the contact of the rotational shaft. Further, it is easy to assemble the brush seal units and also considerably improve the accuracy in the assembly.
A brush seal device of second preferred embodiment according to the present invention is a brush seal device mounted on one of two components that are relatively rotated, for sealing the clearance given between the two components, comprising: a brush seal having piled brush seal units, each having a strip-like brush section on the side facing the other component and having a base plate section on the side opposing the brush section side, the brush section being formed with thin beams each of which is between two slits, and the base plate section being fixed to the one component; a back plate section having a fixing section provided with a positioning pin capable of fitting in the base plate section of the brush seal and having a bearing face for bearing the side face of the brush seal; and a retaining section for retaining, in cooperation with the back plate section, the base plate section of the brush seal; wherein the base plate section of each brush seal unit is provided with positioning sections in which holes are formed by one pitch thereof; each pitch is defined as an interval so that, when the positioning sections of the neighboring brush seal units piled are relatively displaced, the slits and thin beams of the neighboring brush seals overlap each other; and the positioning pin of the back plate section fits in a hole of the positioning sections of the brush seal, thereby to couple the back plate section with the brush seal.
In the brush seal device of the embodiment according to the present invention, neighboring brush seal units are piled such that their positioning sections are relatively displaced by one pitch. Therefore, the slits of one brush seal unit overlap the thin beams of the neighboring brush seal unit, while the beams of the one brush seal unit overlap the slits of the neighboring one.
It is extremely difficult for an assembly machine to pile the brush seal units with the thin fine beams and slits overlapping precisely each other, as specified in design. However, a piling condition effective to sealing ability is easily achieved by displacing one positioning section to the other.
Additionally, it becomes possible to assemble the brush seal exactly and easily without deviation among the brush seal units, by fitting a positioning section to the positioning pin of the back plate section and sandwiching against the retaining section.